The removal or recovery of volatile organic compounds (VOCS) from exhaust gas streams is an important process in environmental engineering. Activated carbon has long been used as an adsorbent in this process, but the presence of moisture in the stream reduces its effectiveness. M.-S. Chou and J,-H. Chiou (J. Envir Engrg ASCE, 123,437(1997)) have studied the effect of moisture content on the adsorption capacities of granular activated carbon (GAC) for normal hexane and cyclohexane in air streams. From their data for dry streams containing cyclohexane, shown in the table below, they conclude that GAC obeys a Langmuir type model in which qvoc.RH=O= abcvoc/(1 + bcvoc)' where q = mVOC/mGAC> RH denotes relative humidity, a the maximum adsorption capacity, b is an affinity parameter, and c is the abundance in parts per million (ppm). The following table gives values of qvOC, RH =O for cyclohexane:
(a) By linear regression of 1/qvoc. RH=O against l/cvoc' test the goodness of fit and determine values of a and b.
(b) The parameters a and b can be related to ∆ads H, the enthalpy of adsorption, and ∆b H, the difference in activation energy for adsorption and desertion of the VOC molecules, through Arrhenius type equations of the form a = ka exp(-∆ads H//RT) and b = kb exp(-∆b H/RT). Test the goodness of fit of the data to these equations and obtain values for ka' kb, ∆ads H, and ∆bH
(c) What interpretation might you give to ka and kb?

WA is the mass adsorbed per unit mass of charcoal.

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33.6°C 0.080 41.5°C c/ppm 57.4°C 76.4°C 99°C 0.052 0.072 0.042 0.027 200 0.069 0.083 0.088 0.056 500 0.093 0.042 0.101 0.063 0.045 1000 2000 0.076 0.083 0.052 0.092 0.068 0.072 0.105 3000 0.112 0.102 0.058 0.087